1. Field of the Invention
The present invention relates to a transmitter, particularly, a transmitter for a remote keyless entry system, for example, which is required to have a certain waterproof function for exclusive outdoor use and to be easy to carry out an operation of exchanging a built-in battery, the operation being necessary even though it is not frequently required.
2. Description of Related Art
A remote keyless entry system is a convenient system in which operating only a push button of a transmitter housed in a case as small as a matchbox allows a door to be locked or unlocked without using any mechanical key. There is also a developed type of system in which no operation of pushing a push button of a transmitter is necessary. In the developed type of system, a door of a vehicle can be locked or unlocked by pushing an entry button of the door of a vehicle with a transmitter putted on. Accordingly, it is not necessary to take out the transmitter from a pocket every time.
Such transmitters are all used outdoors, and thus, a waterproof countermeasure against rain and such is essential. Moreover, they are operated by means of a disposable battery, and therefore, it should be considered whether an operation of exchanging the battery is easy to perform or not.
FIG. 4 shows a first conventional example. FIG. 4 shows a structure similar to the one introduced in Paragraphs [0038] to [0039] in JP-A-11-81762. In FIG. 4, a transmitter 1 includes a main body portion 2, which comprises cases 2a and 2b divided into upper and lower two parts and which is as small as a matchbox, a battery 3, which is housed in a battery housing portion 2d in the main body portion 2 through a battery housing hole 2c formed in a bottom of the case 2a, an O-ring 4 for waterproofing mounted on the periphery of the battery housing hole 2c and a circular rid 5 for closing the battery housing hole 2c with the O-ring 4 inserted therebetween. On a surface of the case 2b (a surface on the back side, which is not shown), provided are various kinds of push button such as a locking button and an unlocking button, for example.
An advantage of the first conventional example is that an operation of exchanging the battery 3 is easy. That is to say, fitting a familiar coin or such in a groove 5a of the circular rid 5 and turning the coin allow the circular rid 5 to be easily taken off. The battery 3 can be thus exchanged without using any special tool.
On the other hand, the first conventional example has following disadvantages. First, the surface of the main body portion 2 has little free space, so that there is only a small space available for sticking an emblem of a manufacturer or a radio frequency identification sticker, for example. This causes little freedom in designing. Namely, on the surface of the case 2a, provided are the battery housing hole 2c and the circular rid 5 while various kinds of push button are provided on the surface of the case 2b, so that an emblem of a manufacturer, a radio frequency identification sticker or such can be stuck only in an extremely small range excluding the above components. This is one of disadvantages. Further, one of waterproofed parts of the transmitter 1 is a part located between the battery housing hole 2c of the case 2a and the circular rid 5. In the case that the O-ring 4 is improperly mounted or fails to be mounted in an operation of exchanging the battery 3, rain water or such would enter from the part, so that a trouble would be caused for an electronic substrate in the main body portion 2. This is another disadvantage.
FIG. 5 shows a second conventional example. FIG. 5 shows a structure similar to the one introduced in Paragraph [0042] in JP-A-2003-201781. In the second conventional example, a transmitter 6 also includes a main body portion 7, which comprises cases 7a and 7b divided into upper and lower two parts and which is as small as a matchbox, similar to the first conventional example described above. There is, however, no “circular rid for exchanging a battery” like the case of the first conventional example described above. The cases 7a and 7b divided into upper and lower two parts are arranged to be able to be disassembled whenever exchange of a battery 8 is necessary. Such a way of exchanging a battery is called a “case disassembling type”.
In an inner surface of the case 7a, provided are a spring characteristic terminal 7c in contact with one electrode of a battery 8, a conductive sheet 7d electrically connected to the spring characteristic terminal 7c and a waterproof seal 7e on the periphery of an opening of the case 7a. On the other hand, in an inner surface of the case 7b, provided are a spring characteristic terminal 7f in contact with the other electrode of the battery 8, an electronic substrate 9 on which a predetermined electronic circuit is mounted, the electronic circuit using as a power source a terminal voltage of the battery 8 supplied through the above two spring characteristic terminals 7c and 7f to operate, and a holding body 10 for holding the periphery of the battery 8 to perform positioning.
In the second conventional embodiment, there is no circular rid for exchanging a battery, so that enough free space is secured on the surface of the main body portion 7. This leads to an advantage that the freedom for sticking an emblem of a manufacturer, a radio frequency identification sticker or such is large. Moreover, there is another advantage that elastic fitting (snap connection) between the cases 7a and 7b divided into upper and lower two parts allows the main body portion 7 to be easily disassembled by means of a coin or a nail in some cases, for example, without any special tool, so as to easily exchange the battery 8. Further, there is only one waterproof part between the cases 7a and 7b divided into upper and lower two parts (a waterproof seal 7e). Accordingly, fixed adhesion of the waterproof seal 7e prevents the waterproof seal 7e from coming off in an operation of exchanging the battery 8. This is also an advantage of the second conventional example. Many recent transmitters for a remote keyless entry system are, thus, of the case disassembling type because of the above advantages.
The above second conventional example (a case disassembling type of transmitter) has superior advantages that the freedom for sticking an emblem of a manufacturer, a radio frequency identification sticker or such is large, that battery exchange is easy and that a waterproof performance can be maintained. In the second conventional example, however, the cases 7a and 7b divided into upper and lower two parts are disassembled for exchanging the battery 8, so that the electronic substrate 9 sometimes comes off in an exchanging operation. In order to avoid the above, it is possible in some cases to take measures so that the electronic substrate 9 would be fixed to the case 7b by means of a screw 11, as shown in FIG. 5, for example. Such a measure by means of a screw, however, is not preferable since it causes a complicated manufacturing process.
FIG. 6 shows a third conventional example in which a structure is improved with respect to the above disadvantages. FIG. 6 is a sectional view of an integral part of a structure in assembling a transmitter, the structure being similar to the one introduced in Paragraphs [0012] to [0015] in JP-A-2001-339176. In FIG. 6, an elastic piece 12a of an inner case 12 is first engaged with a periphery of the electronic substrate 9 to fit the electronic substrate 9 and the inner case 12 into a sealing rubber 13 with the engagement maintained. The assembled body (the electronic substrate 9+the inner case 12+the sealing rubber 13) is then pushed into the case 7b so that a protrusion 13a of the sealing rubber 13 (a pressure deformation part formed by a convex portion 12b of the inner case 12) would engage with a hollow 7g on an inner circumferential side surface of the case 7b. Such assembling finally allows the case 7b, the sealing rubber 13, the inner case 12 and the electronic substrate 9 to be formed into one body, so that the electronic substrate 9 does not come off in exchanging a battery.
In the above third conventional example, however, the electronic substrate can be prevented from coming off in exchanging a battery while the following disadvantage may be caused. That is to say, large friction occurs between the protruded portion 13a of the sealing rubber 13 and a protruded portion 7f of the case 7b in fitting the electronic substrate 9 and the inner case 12 into the sealing rubber 13, and thereby, damage such as breakage of a friction part of the sealing rubber 13 may be caused in some cases.
In view of the above, the invention relates to a structure capable of certainly preventing an electronic substrate from coming off in exchanging a battery by disassembling a case and is to provide a transmitter, which allows the structure to be put into practice without causing a complicated manufacturing process and any damage of a sealing rubber.